OBJECTIVE: To evaluate and refine biochemical tests that would predict the hormonal responsiveness of breast tissue. APPROACH: Human breast tissues and selected rodent mammary tumors are being investigated to better define properties of neoplasms that might predict their biological behavior. The two rodent systems are: DMBA-induced mammary adenocarcinomas, arise in situ and are largely dependent on estrogen, prolactin and insulin (a smaller number are independent and grow in the absence of hormones); R3230AC mammary adenocarcinomas, transplantable to isologous rats, are autonomous but responsive (growth-inhibited) by administration of the above hormones. Both models are used to gain information as to estrogen receptors, as well as receptors for other steroid and polypeptide hormones and for studies of metabolic control by these hormones.